Rotor structure for turbo machines

ABSTRACT

In a built-up rotor structure employing a long thru-bolt as in multistage gas compressors and turbines, a support sleeve is fixed on the bolt passing through the assembly of wheels. A second sleeve is fixed within the assembly of wheels and has an interlocking connection with the support sleeve which serves to restrain the thru-bolt from becoming eccentric to the wheel assembly, and to increase the natural frequency of the bolt to avoid operation at resonant conditions. The structure nevertheless accommodates normal radial growth of the individual parts due to centrifugal forces and temperature changes, and axial growth due to temperature changes.

United States Patent Hansen et al.

[451 Aug. 1, 1972 [54] ROTOR STRUCTURE FOR TURBO MACHINES [72] Inventors: Raymond E. Hansen, New Alexandria; Eugene L. Huesgen, Jeanette,

both of Pa.

[73] Assignee: Carrier Corporation, Syracuse, NY.

[22] Filed: Oct. 7, 1970 [21] Appl. No.: 78,728

52 us. c1 ..4l6/l98, 416/199 [51] Int. Cl ..F0ld 5/06 [58] Field of Search..4l6/l98, 198A, 199,200, 201, 416/204, 244 A, 134, 136, 138, 198

[56] References Cited UNITED STATES PATENTS 3,304,052 2/1967 Warner et al. ..41 5/1 34 3,356,339 12/1967 Thomas et a1 ..416/244 A 1,551,402 8/1925 Junggrew ..4l6/198 A FOREIGN PATENTS OR APPLICATIONS 586,200 3/ 1947 Great Britain ..415/ l 34 Primary Examiner-Everette A. Powell, Jr.

Assistant Examiner-Clemens Schimikowski Att0rney--Harry G. Martin, Jr. and J. Raymond Curtin 57 ABSTRACT In a built-up rotor structure employing a long thrubolt as in multistage gas compressors and turbines, a

support sleeve is fixed on the bolt passing through the assembly of wheels. A second sleeve is fixed within the assembly of wheels and has aninterlocking connection with the support sleeve which serves to restrain the thru-bolt from becoming eccentric to the wheel assembly, and to increase the natural frequency of the bolt to avoid operation at resonant conditions. The

structure nevertheless accommodates normal radial growth of the individual parts due to centrifugal forces and temperature changes, and axial growth due to temperature changes.

4 Claims, 4 Drawing Figures FIG.4

IN TOR. RAYMOND E. NS m, EUGENE L. H UESG ATTORNEY ROTOR STRUCTURE FOR TURBO MACHINES BACKGROUND OF THE INVENTION In the manufacture of turbomachines of the multistage type, as centrifugal compressors, axial flow compressors and turbines, there are advantages in employing rotors of the composite structure, wherein the wheels are arranged in stack formation between stub shafts, which are fixed to the ends of a thru-bolt, sometimes referred to as a tie-bolt. The wheel members in centrifugal gas compressors take the form of impellers. In turbines and axial flow compressors, the wheels consist of bladed disks. The wheel assembly has an axially extending bore passage having clearance with the thrubolt.

This form of rotor structure results in the thru-bolt being of substantial length. Such long bolts have inherent problems associated with bolt resonance, and rotor imbalance, caused mainly by deflection or radial displacement of the bolt. The situation is aggravated by the high speed at which the rotor structure operates.

This invention has as an object a structure which maintains the thru-bolt centered within the rotor structure, and serves to stiffen the thru-bolt to increase the natural frequency thereof to avoid resonance at operating conditions.

SUMMARY OF THE INVENTION A thru-bolt support sleeve member is fixed to the bolt in the medial area thereof as by shrink fit. The sleeve is located within the bore passage of the wheel assembly and has close initial clearance therewith. A second sleeve member is also positioned intermediate the thru-bolt and the bore passage of the assembly. The second sleeve is fixed to one of the members of the assembly, as by shrink fit, and has running clearance with the bolt. The two sleeve members have interlocking portions which serve to prevent radial displacement of the thru-bolt relative to the impeller, wheel assembly, or other part to which it may be attached.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a foreshortened lengthwise sectional view of a rotor structure in which our invention is incorporated;

FIG. 2 is an enlarged sectional view of the seal member and contiguous portion of the thru-bolt as shown in the upper center portion of FIG. 1;

FIG. 3 is an enlarged view in perspective of the support sleeve which is fixed to the thru-bolt; and

FIG. 4 is a view similar to FIG. 3 of the sleeve member fixedly mounted within the seal sleeve.

, DESCRIPTION OF THE PREFERRED EMBODIMENT The composite rotor structure shown, as an example in FIG. 1, is incorporated in a multistage twin type centrifugal gas compressor. The rotor includes stub shafts 10, 11 fixedly secured to the ends of the thru-bolt 12. A group 13 of impellers is positioned about the end por-i tion of the thru-bolt attached to the stub shaft 10, and a second group 14 of impellers is mounted in proximity to the stub shaft 11.

A cylindrical seal member 17 is positioned intermediate the groups of impellers 13,14. In the foreshortenedview, FIG. 1,- only the first and last stage impellers 18,19 are shown in the group 13, and in like manner, the first and last stage impellers 20,21 in the group 14.

The impellers abutting against the stub shafts 10,11 are impellers 18 and 20, and the stub shafts are formed with shoulder structures 25. Also, the abutting areas between the respective impellers are formed with similar shoulder areas 27. Also, there is a shoulder engagement 30 between the ends of the seal member 17 and the adjacent impellers 19,21. The shoulder structures 25,27,30 serve to center the impellers and the seal member 17, maintaining the impellers and the seal member in coaxial alignment. Driving means in the form of pins 31 are positioned intermediate the impellers and stub shafts and seal member 17, the pins 31 serving to provide a driving connection to the impellers.

In the assembled form, the stub shafts 10,11 are threaded onto the ends of the thru-bolt 12 whereby the impellers and sleeve member 17 are compressed axially to form a rigid structure for rotationin unison.

As previously stated, the thru-bolt 12 is of appreciable length, especially in view of the fact that the compressor is of the multistage type, and furthermore, is of the twin type having the separated impeller groups 13 and 14. Such long thru-bolts result in bolt resonance and imbalance at the high speeds at which these rotor assemblies are operated. This invention is directed to a structural arrangement wherein deflection or radial displacement of the thru-bolt is prevented, the bolt being maintained centered with the rotor structure, and also stiffened to increase the natural frequency of the bolt which avoids resonance thereof at operating speeds.

A support sleeve 37 is fixedly mounted on the thrubolt as by being shrunk thereon. Other than the area contacted by the bolt, the bore 40 of the support sleeve has clearance with the periphery of the shaft 12, see FIG. 2. The support sleeve 37 also has a slight clearance with the bore of the seal member 17.

A second sleeve member 43 is fixedly mounted in the seal 17. This sleeve 43 is formed with a shrink fit in the areas 44,45. The bore 47 of the sleeve 43 also has clearance with the thru-bolt 12.

The sleeves 37,43 are formed with interlocking portions. Referring to FIG. 3, the sleeve 37 is formed with four notches 48 extending inwardly from the end of the sleeve confronting the sleeve 43. The sleeve 43 is formed with axially extending projections 50. The projections 50 are dimensioned and spaced complemental to the notches 48 in sleeve 37, whereby the sleeves 37,43 are interlocked, and it will be apparent that this interlocking structure prevents radial displacement between thru-bolt 12 and the seal member 17. While this arrangement maintains the thru-bolt centered in the impeller assembly, it permits and accommodates radial and axial growth of the parts, as shaft 12, seal member 17, and sleeves 37,43, as by temperature change and centrifugal force.

In brief, the rotor structure is assembled by arranging the impeller in the groups 13,14 in stack formation. The support sleeve 37 is heated and positioned on the thru-bolt 12 with the end of the sleeve engaging the shoulder 51 formed on the bolt 12. Upon cooling, the sleeve has a tight shrink fit with the bolt.

The bolt with the sleeve 37 shrunk thereon, is threaded into the stub shaft 10. The stack of impellers in the group 13 is sleeved over the bolt against the stub shaft 10. The seal member 17 is heated and passed over the sleeve 37 in abutting relation with the impeller 19, thereupon the sleeve 43 is positioned in the seal member 17 with the cylindrical portion 45 thereof abutting against the shoulder 55 formed in the bore of the member 17. The stack of impellers 14 is then positioned against the seal 17 and the stub shaft member 1 1 is threaded on the thru-bolt. A procedure is employed in this last step which results in the compression of the impeller assemblies and seal member 17 being of predetermined value. When the stub shaft 11 is tightened to produce the desired compressive force on the impeller assembly, keys 56 are inserted between the hub of impeller 20 and the stub shaft 11. Accordingly, the stub shafts 10,-11, sleeve 17 and impellers are fixed together for rotation in unison.

Upon cooling of, the seal member 17, a shrink fit is effected with the sleeve 43. With this structure, the sleeve 37 is fixedly secured to the thru-bolt l2 and the sleeve 43 is fixedly secured within the seal 17. However, assembly of the rotor structure was convenient due to the provision of the slight clearance between the outer diameter of the sleeve 37 andthe bore of the seal 17, and also the greater clearance between the bore of the sleeve 43 andthe outer diameter of the thru-bolt 12. Yet, the notch and projection arrangement 48,50 prevents any relative radial displacement between the sleeve members and, accordingly, between the thrubolt 12 andthe rotor structure, maintaining concentricity of these parts, while permitting symmetrical relaand contraction of the parts.

While we have described and illustrated a preferred embodiment of the invention, it will be understood the invention is not limited thereto since it may be otherwise embodied within the scope of the following claims.

WE CLAIM:

l. A rotor structure comprising a thru-bolt, a stub shaft fixed to each end of said thru-bolt, an assembly of wheels mounted intermediate said stub shafts and being fixedly secured thereto, said rotor structure also including a seal sleeve member disposed in the center area of said wheel assembly and fixedly secured thereto, said assembly being formed with a bore passage spaced concentrically about said thru-bolt, a support sleeve member fixed to said thru-bolt and having clearance with said bore passage, a second sleeve member mounted in said borepassage, said second sleeve being disposed axially of said support sleeve and being fixedly secured to said seal sleeve member, said second sleeve member encircling said thru-bolt in concentrically spaced relation thereto, the confronting ends of said sleeves being formed with interlocking means operable to restrain said thru-bolt from radial displacement relativ to said second sleeve ember.

A structure as set for fh in claim 1 wherein said 1nterlocking means is formed with engaging portions permitting relative axial movement between said support sleeve and said second sleeve.

3. A structure as set forth in claim 1 wherein said interlocking means is formed with engaging portions permitting change in radial dimension in said seal sleeve member, thru-bolt and support sleeve and second sleeve due to change in temperature or centrifugal force.

4. A structure as set forth in claim 1 wherein one of said sleeve members is formed at the end thereof confronting said other sleeve member with a plurality of notches spaced apart circumferentially, said other sleeve member being formed with axially extending projections positioned in said notches. 

1. A rotor structure comprising a thru-bolt, a stub shaft fixed to each end of said thru-bolt, an assembly of wheels mounted intermediate said stub shafts and being fixedly secured thereto, said rotor structure also including a seal sleeve member disposed in the center area of said wheel assembly and fixedly secured thereto, said assembly being formed with a bore passage spaced concentrically about said thru-bolt, a support sleeve member fixed to said thru-bolt and having clearance with said bore passage, a second sleeve member mounted in said bore passage, said second sleeve being disposed axially of said support sleeve and being fixedly secured to said seal sleeve member, said second sleeve member encircling said thru-bolt in concentrically spaced relation thereto, the confronting ends of said sleeves being formed with interlocking means operable to restrain said thrubolt from radial displacement relative to said second sleeve member.
 2. A structure as set forth in claim 1 wherein said interlocking means is formed with engaging portions permitting relative axial movement between said support sleeve and said second sleeve.
 3. A structure as set forth in claim 1 wherein said interlocking means is formed with engaging portions permitting change in radial dimension in said seal sleeve member, thru-bolt and support sleeve and second sleeve due to change in temperature or centrifugal force.
 4. A structure as set forth in claim 1 wherein one of said sleeve members is formed at the end thereof confronting said other sleeve member with a plurality of notches spaced apart circumferentially, said other sleeve member being formed with axially extending projections positioned in said notches. 